Many of commercial, industrial, household, and personal care products are designed to mask malodor in the environment to which they are applied or in which they are used. Products may also generate malodor during and/or upon application or use or may themselves be inherently malodorous due to their constituents and functional raw ingredients.
Malodor inherent to cosmetic, industrial and household formulations is an extensive and ubiquitous problem common to many different applications ranging from household cleaners to personal care products including antiperspirants, deodorants, sunless tanners, hair colorants, shampoos and conditioners, hand and body lotions, hair perming and relaxing agents, and the like.
Permanent hair colorants are some of the most challenging formulations to fragrance since they contain ammonia. Due to ammonia's physical properties, such as very high vapor pressure, and its very pungent and offensive perceived olfactive profile, it is considered one of the most difficult malodors to cover using targeted malodor covering perfumery. Semi-permanent or demi-permanent hair colorants contain various substituted amines, sometimes with ammonia present in addition.
Permanent and demi-permanent hair coloring products contain various degrees of ammonia concentrations along with different types of primary, secondary and tertiary amines. Ammonia is an integral part of permanent hair coloring since its numerous roles include: the swelling and the softening of hair to help individual dyes penetrate the hair cuticle into the cortex; acceleration of the oxidative polymerization of colorants by raising the pH inside the hair; activation of the peroxide to activate bleaching and hence, achieve “lifting” of the existing hair color.
Covering the perception of ammonia in products, such as permanent hair coloring products, remains a formidable task despite numerous attempts at creating ways and methods to do so. The difficulty to cover ammonia lies in the necessity to cover ammonia physically rather than chemically since the creation of any type of chemical bond between ammonia and another odorant or chemicals in the formulation will result in a less performing, and sometime even unstable product.
Cosmetic hair colorants referred to as “level 2” are one way to reduce the consumer's exposure to ammonia and its malodor by introducing substituted amines as alkalizing agents in lieu of ammonia. The substituted amines are sometimes used in combination with lower concentrations of ammonia to help these seemingly less harsh formulations in the lifting of existing hair color. Unfortunately, these products do not achieve the results obtained using a true permanent hair coloring system based on ammonia. Some of the disadvantages of a non permanent hair color formulation are less color lift, less dye take and faster fading of the colorants.
Other systems are available and are marketed as a safer alternative to ammonia hair colorants. Alternative available alternative formulations are based on auto-oxidative dyes. Other marketed safer products are in the form of powdered mixtures made of solid dyes (usually in their sulfated form) along with a solid oxidant (typically sodium perborate) activated by the addition of water. These products often result in very drab colors and give the consumer a limited palette of colors.
There remains a need to provide ammonia malodor masking in products such as permanent hair colorants without losing the benefits of the ammonia component, namely its ability of dye uptake and hair color lifting.
Methods of covering ammonia malodor known in the art have been limited to empirical observations and explanations of narrow physico-chemical mechanisms, whereby fragrance materials are chosen to cover malodor based on their hedonic performance.
For instance, U.S. Pat. No. 6,403,075 addresses fragrance materials with a phenyl ring moiety and air diffusion coefficient larger than 5.7 and/or odorants with C-5 ring moiety with at least sp2 hybridized C that were empirically observed to be good ammonia masking agents. In U.S. Patent Application No. 2002/0058017A1, cis-3-hexenol was determined to empirically mask ammonia well in permanent hair coloring systems based on empirical observations.